Add proper cache headers & file date to GETTILEIMAGE response

[zspitzer]

Two anonymous valid requests for a tile from the tilecache will retrieve the same file twice

Adding the cached file date to the responce header will help and cache headers

Combining this with RFC 11 and USERNAME=Anonymous will enable a normal proxy server to cache the requests.

To full take advantage of this viewers would need to check if anonymous access is available first for base layers for public sites. It would still work using basic for intranet type environments, it's the session in the url which creates the problem

[jbirch]

You'd also want to add 304 / if-modified-since handling to the MapAgent I think...

[jbirch]

Removing version from enhancement request. If this enhancement request has been addressed or is no longer required, please close ticket.